Hydraulic press



May 15, 1951 F. J. TRGZMULLE R 5 5 HYDRAULIC PRESS Filed Dec. 29, 1948 2 Sheets-Sheet 1 19 IWHH 1 Invanran 8,, M, HWY-60m May 15, 1951 F. J, TROZMULLER HYDRAULIC PRESS 2 Sheets-Sheet 2 Filed Dec. 29, 1948 I INVcuroR Patented May 15, 1951 HYDRAULIC PRESS Friedrich Josef Triizmiiller, Vienna, Austria,

assignor to Semperit oesterreichisch-Amerikanische Guminiwerke Aktiengesellschaft,

Vienna, Austria Application December 29, 1948, Serial No. 67,948 In Austria January 23, 1948 5 Claims. 1

This invention relates to improvements in hydraulic presses with pressure regulation, particularly for die-stamping purposes.

In hydraulic presses hitherto employed, in general and also for die-stamping purposes, the elements requisite for driving the press, the pump, fluid reservoir and conduits, as well as the control devices were disposed outside the press and in consequence gave rise to various disadvantages, such as complicated construction, large space requirements, loss of fluid by leakage, pollution, troublesome maintenance and high working costs. In addition, in such design owing to the resistance which the fluid meets in the long conduits a considerable part of the energy is converted into heat. This energy loss must be compensated for by augmenting the pump drive.

An object of the invention is the construction of a hydraulic press for the stamping of matrices, clichs and the like, in which all of the foregoing disadvantages are avoided, the complete fluid-impelling parts being housed together with a pressure regulator of the simplest type within the pump piston itself, which also serves as the fluid reservoir.

Another object is to provide a simple, cheap and Workmanlike construction of such a hydraulic press.

h A still further object is to obtain a considerable economy of space and motive power and a continuous automatic lubrication of all parts of the press unit.

These and other objects, made clear during the further progress of this specification, are

effected by means of my invention, a full and complete understanding of which is facilitated by reference to the drawings herein, in which:

Fig; l is a vertical cross-section, taken along the line I-I of Fig. 3, also showing the pressure increase regulator, the high pressure regulator and the safety valve in section.

Fig. 2 is a vertical cross-section, taken along the line II-II of Fig. 3; and

Fig. 3 is a horizontal cross-section, taken along the line III-III of Fig. 2.

Referring to the drawing there is disposed in the pressure cylinder I the hollow piston 2 carrying the stamping ram lit, the cavity 2 of this piston, according to the invention, serves as an oil reservoir and is closed at its upper part by a perforated plate 20. In the piston chamber is located a two-pump reversible pump unit 3, 4, for example, a toothed wheel or rotary unit. The pump 3 is constructed for low pressure and high output whereas the pump 4 works with high pressure and low output. This unit is driven by a motor I located on the outside of the press cylinder I through the enclosed bevel wheels 6, 6' and axle 5, on which is displaceably mounted by slot 2! and key 22 the appropriate bevel Wheel 6. The pressure channel 3a of the pump 3 is placed in temporary communication with the channel 9a opening into the piston base through the control slide valve 8. The control slide valve 8 has, for this purpose, a corresponding long-channel 9 which also communicates with the oppositely disposed channel Ill by abore 23. The channel it can, by movement of the control slide valve be placed in overlapping relationship with the outlet is I. The under surface of the control slide valve 8 is influenced by the oil pressure in the working chamber 24 of the cylinder land on its upper surface bears the spring I2, the pressure of which can be adjusted by the regulating-screw 25. Movement of the slide valve is limited by a pin it which projects into a groove 13', of the appropriate length, in the control slide valve 8.

The extension of the pressurechannel to of the pump 4 opens directly into the piston base.

For regulation of pressure increase there is provided an adjustable needle valve [4 whose inlet communicates with a pipe 15 terminating in the piston base. The outlet communicates through the telescopic pipe !6 with the gear box 26 of the bevel wheels 6, 6', which is thus continuously automatically lubricated. The oil flowing through the gear box runs back again through a bore 2'! in the base of the gear box 2'6 into the I piston chamber. For the adjustment and maintenance of the desired highest pressure there is also provided:

the pressure chamber 24 of the cylinder I through a pipe l8.

The working of the press falls into two sections and in the first section occurs in fact a rapid upward movement of the piston 2 at low pres-.,

sure until the stamping ram l9 reaches the stamping position, whereupon follows a rapid increase of its pressure until the highest pressure requisite for the stamping process is reached.

When the motor I is switched on it drives the pump unit 3, 4 through the bevel wheel 6, 5,

ber 24 of the cylinder. The high output of the low pressure pump 3 effects in this period a rapid upward movement of the piston 2, at a pressure which is necessary to overcome the dead weight of the piston, the weight of its contents and the frictional resistance. When the piston arrives at the stamping position, the pressure in the cylinder increases until it overcomes the pressure of the spring l2 bearing on the control slide valve 8. The slide valve is now elevated, the channel 9a closed, whereupon communication between the pressure channel 3a of the low pressure pump 3 and the outlet H is effected thus short-circuiting the low pressure pump. From this moment on, only the high pressure pump 4 comes into play and so there is a rapid pressure increase depending on the predetermined setting of the needle valve M. According to the magnitude or the adjustable valve passage there flows back a determined amount of pressure 011 through the bevel wheel housing 28 and the bore 2'! into the piston chamber 2 whereby the duration of the pressure increase for the stamping process is controlled up to the arrival of the highest pressure. When the desired highest pressure is reached the likewise adjustable high pressure regulator 'l'l comes into action, which permits such a quantity of the pressure oil to flow back into the piston chamber per unit of time that the attained highest pressure remains maintained.

The safety valve 18 is so adjusted that it only operates when the highest pressure is exceeded.

The pressure within the pressure chamber 24 may be observed on the pressure gauge 28, the pipe 28' of which communicates with the pressure chamber '24.

When the requisite stamping pressure period has expired the driving motor 7 is switched into reverse movement by means of an electrical time switch. The high pressure pump 4 now draws out the pressure oil from the inner chamber of the cylinder and drives it back into the piston chamber whereupon commences the downward motion of the piston 2. When the pressure in the cylinder falls below the pressure adjusted through the spring [2, the slide valve 8 returns to its initial position and the hitherto shortcircuited low pressure pump 3 participates in the drair'iage of the pressure oil from the cylinder chamber into the piston chamber. The piston 2 now drops rapidly back 'to its initial position, whereupon the driving motor '1 is switched oii.

WhatI claim as my invention and wish to secure by Letters Patent is:

l. A hydraulic press with pressure regulation comprising a pressure cylinder, a hollow pressure piston slidably arranged in the said cylinder, the cavity of said piston serving as a reservoir for the pressure fluid, a low-pressure, high-capacity, gear pump the outlet of which communicates with the pressure chamber of said cylinder, a high-pressure, low-capacity, gear pump the outlet of which communicates with the pressure chamber, said pumps being arranged in parallel between the piston cavity and the pressure chamber, a reversible motor and gearing for All driving said pumps, and a by-pass slide valve arranged in the pressure passage of the lowpressure pump and controlled on the one hand by an adjustable reaction pressure means and on the other hand by the working pressure in the pressure chamber, said by-pass valve being adapted to by-pass the low-pressure pump by discharging its output into the piston cavity ur a.)

Iii:

cylinder, a high-pressure, low-capacity,

I when the working pressure exceeds the set reaction pressure, the pumps, the bypass valve and the gearing being arranged in the cavity of the hollow pressure piston.

'2. A hydraulic press with pressure regulation comprising a pressure cylinder, a hollow pressure piston slidably arranged in the said cylinder, the

cavity of said piston serving as a reservoir for the pressure iiuid, a low-pressure, high-capacity, gear pump the outlet of which communicates with the pressure chamber of said cylinder, a high-pressure, low-capacity, gear pump the outlet of which communicates with the pressure chamber, said pumps being arranged in parallel between the piston cavity and the pressure chamber, a reversible motor and gearing for driving said pumps, and a by-pass slide valve arranged in the pressure passage of the lowpressure pump and slidably arranged in the bottom of the hollow pressure piston, and having a front face exposed to the pressure chamber and another face which is loaded by the pressure of an adjustable spring, said by-pass valve being adapted to by-pass the low-pressure pump by discharging its output into the piston cavity when the working pressure exceeds the spring pressure, the pumps, the by-pass valve and the gearing being arranged in the cavity of the hollow pressure piston.

3. A hydraulic press with pressure regulation comprising a pressure cylinder, a hollow pressure piston slidably arranged in the said "cylinder, the cavity of said piston serving as a reservoir of the pressure fluid, a low-pressure, highcapacity, gear pump the outlet of which communicates with" the pressure chamber of said gear pump the outlet of which communicates with the pressure chamber, said pumps being arranged in parallel between the piston cavity and the pressure chamber, a reversible motor and gearing for driving said pumps, and a by-pass slide valve arranged in the pressure passage of the low pressure pump and controlled on the one hand by an adjustable reaction pressure means and on the other hand by the working pressure in the pressure chamber, said slide valve having channels communicating with each other, one of which connects the low-pressure pump with the pressure chamber of the cylinder while the other comes into overlapping relationship with an outlet opening into the piston cavity for by-passing the low-pressure pump by discharging its output into the piston cavity when the working pressure exceeds the set pressure, the pumps, the 'by-pass valve and the gearing being arranged in the cavity of the hollow pressure piston.

4. A hydraulic press with pressure regulation comprising a pressure cylinder, a hollow pressure piston slidably arranged in the said cylinder, the cavity of said piston serving as a reservoir for the pressure fluid, a low-pressure, highcapacity, gear pump the outlet of which communicates with the pressure chamber of said cylinder, a high-pressure, low-capacity, gear pump the outlet of which communicates with the pressure chamber, said pumps being arranged in parallel between the piston cavity and the pressure chamber, a reversible motor and gearing for driving said pumps, a by-pass slide valve arranged in the pressure passage of the lowpressure pump and controlled on the one hand by an adjustable reaction pressure means and on the other hand by the working pressure in the pressure chamber, said by-pass valve being adapted to bypass the low pressure pump by discharging its output into the piston cavity when the working pressure exceeds the set reaction pressure, and a safety valve communicating with the pressure chamber, the pumps, the by-pass valve, the gearing and the safety valve being arranged in the cavity of the hollow pressure piston.

5. A hydraulic press with pressure regulation comprising a pressure cylinder, a hollow pressure piston slidably arranged in the said cylinder, the cavity of said piston serving as a reservoir for the pressure fluid, a low-pressure, highcapacity, gear pump the outlet of which communicates with the pressure chamber of said cylinder, a high-pressure, low-capacity, gear pump the outlet of which communicates with the pressure chamber, said pumps being arranged in parallel between the piston cavity and the pressure chamber, a reversible motor and gearing for driving said pumps, a by-pass slide valve arranged in the pressure passage of the low-pressure pump and controlled on the one hand by an adjustable reaction pressure means and on the other hand by the working pressure in the pressure chamber, said by-pass valve being adapted to by-pass the low-pressure pump by discharging its output into the piston cavity when the working pressure overcomes the set reaction pressure, an adjustable pressure increase regulator communicating with the pressure chamber of the cylinder, the setting of said regulator controlling the pressure increase, a housing for said gearing, a conduit between said pressure increase regulator and said housing for leading the pressure fluid escaping from the pressure increase regulator into the housing of the gearing, and a safety valve communicating with the pressure chamber, the pumps, the by-pass valve, the pressure increase regulator, the gearing with its housing and the safety valve being arranged in the cavity of the hollow pressure piston.

FRIEDRICH JOSEF TRCZMULLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 876,920 Weeks Jan. 14, 1908 947,613 Gathmann Jan. 25, 1910 2,061,530 Wile Nov. 17, 1936 2,136,080 Joy Nov. 8, 1938 2,308,731 White Jan. 19, 1943 2,342,311 Thompson Feb. 22, 1944 

